A distributed data communication network is a hierarchical system of hardware components arranged so that each hardware device is connected, directly or indirectly, to every other device. At the lowest level are user terminals or hosts, which form part of the access network. These terminals are linked to one or more concentrators, a statistical multiplexer often with protocol converters and several low data rate output lines and a fewer number of high data rate output data lines. The concentrators form the second level of the hierarchy and, together with the terminals, form the access network.
The concentrators, which may be connected to other concentrators in a hierarchical fashion, are ultimately connected to the backbone, which forms the highest level in the hierarchy. The backbone consists of high speed, high capacity links that terminate at backbone nodes. A backbone node consists of one or more devices, and includes a switching device for routing traffic within the backbone. The data traffic from the concentrators enters the backbone at a backbone node.
Existing methods for utilizing a distributed data communication network have deficiencies that are overcome by the present invention. Some of these methods were only capable of evaluating each level of the hierarchy independently of all the others. For example, the topology of the backbone links connecting the backbone nodes would be arranged for optimal performance independently of the access network. This method, whereby each level of the hierarchy is optimized independently of all the others, does not necessarily produce a distributed data communication network that operates most economically or efficiently.
Other so called vendor-specific methods can only be used to design a distributed data communication network with equipment provided by a limited number of vendors, and in many cases with equipment provided by only a single vendor. Still other generic methods, while not limited to specific vendors' hardware, do not address the hardware capabilities with sufficient detail to permit the selection of particular hardware components. Finally, other existing methods can only be used to design backbone links composed of T1 links or 56 Kbps links, but not a hybrid of both.